Addition of Lithium Silylamides to 1,2-Dicyanobenzene: Isoindoline-1,3-diimine Derivatives Investigated by NMR/XRD/DFT Approach

Abstract

Phthalocyanines and their building blocks, isoindoline-1,3-diimines (diiminoisoindoles, DIIs), represent a structurally diverse class of compounds with the ability to make metal complexes and perform in various fields from medicine to photovoltaics and homogeneous catalysis. According to the present study, monosubstituted diiminoisoindoles, their higher homologues, and complexes can be effectively prepared by addition of silylated lithium amides to 1,2-dicyanobenzene followed by mild protonolysis or a condensation. An addition of DII to carbodiimides or reactions of lithiated DIIs with acyl chlorides give DII-guanidines and amido derivatives. The imino group of the amido derivatives is preferentially and quantitatively reduced by sodium borohydride. Dynamic behavior and structure of all studied classes of compounds were investigated from the stereochemical point of view─possible E/Z-isomerization and dimerization (DIIs and amido derivatives), tautomerism (guanidines), and stability both in solution and in solid state. The resonance-assisted hydrogen bonds are present in all species except reduced amides, predetermining them to be exceptional ligands in coordination chemistry.